421870021 has 2 divisors, whose sum is σ = 421870022. Its totient is φ = 421870020.

The previous prime is 421869949. The next prime is 421870037. The reversal of 421870021 is 120078124.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 350213796 + 71656225 = 18714^2 + 8465^2 .

It is a cyclic number.

It is not a de Polignac number, because 421870021 - 2¹⁷ = 421738949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (421870621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210935010 + 210935011.

It is an arithmetic number, because the mean of its divisors is an integer number (210935011).

Almost surely, 2^421870021 is an apocalyptic number.

It is an amenable number.

421870021 is a deficient number, since it is larger than the sum of its proper divisors (1).

421870021 is an equidigital number, since it uses as much as digits as its factorization.

421870021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 421870021 is about 20539.4747011699. The cubic root of 421870021 is about 749.9970494699.

The spelling of 421870021 in words is "four hundred twenty-one million, eight hundred seventy thousand, twenty-one".